The "OMG, the cows have guns!" argument has reared its head a few times on the Blizz boards. Basically the only reason anyone has for claiming that the Tauren should not have guns is that they compared them to the Native Americans, who of course they use bows! Never mind that once given access to firearms, the Plains Indians took to them rather fondly. They are a superior hunting tool, aside from the noise they make, and at Custer's Last Stand, most of the Caucasians killed there were not shot by arrows. So the bows & Indians stereotype doesn't necessarily work.
Besides, while seeing a cow with a gun is funny, wouldn't a cow with a bow look even weirder?